Surfactant-stabilized emulsion increases gentamicin elution from bone cement.

Abstract

Liquid antimicrobial use for antimicrobial-loaded bone cement is limited because of decreased strength and small volume that can be loaded. Emulsifying the liquid antimicrobial into the monomer may address both issues. We determined the effect of using a surfactant-stabilized emulsion on antimicrobial release, compressive strength, and porosity. We made 144 standardized test cylinders from emulsified antimicrobial-loaded bone cement (three batches, 72 cylinders) and control antimicrobial-loaded bone cement made with antimicrobial powder (three batches, 72 cylinders). For each formulation, five specimens per batch (n = 15) were eluted in infinite sink conditions over 30 days for gentamicin delivery; five specimens per batch were axially compressed to failure after elution of 0, 1, and 30 days (n = 45); and two noneluted specimens and two gentamicin delivery specimens from each batch (n = 12) were examined under scanning electron microscopy for porosity. Antimicrobial release and compressive strength were compared across cement type and time using repeated-measures ANOVA. Emulsified antimicrobial-loaded bone cement released four times more antimicrobial than control. Compressive strength of emulsified antimicrobial-loaded bone cement was less than control before elution (58.1 versus 81.3 MPa) but did not decrease over time in elution. Compressive strength of control antimicrobial-loaded bone cement decreased over 30 days in elution (81.3 versus 73.9 MPa) but remained stronger than emulsified antimicrobial-loaded bone cement. Porosity was homogeneous, with pores ranging around 50 μm. Emulsified antimicrobial-loaded bone cement has homogeneous porosity with increased drug release but a large loss of strength. Liquid antimicrobials are released from emulsified antimicrobial-loaded bone cement, but increased strength is needed before this method can be used for implant fixation.